The Future “Golden Age” of Predictive Models for Surface Water Quality and Ecosystem Management

Abstract

This paper is based on a Simon W. Freese lecture given at the ASCE North American Water and Environment Congress '96, Anaheim, Calif., on June 24, 1996. The role of water quality modeling in providing input to the decision-making process through understanding, dialogue, and consensus is discussed. The evolution of models is seen in three stages. During the first stage (1925 to about 1980), all sources (point, nonpoint, and sediment) were external to the model, but only point sources were directly linked to the originating input. During the second stage (about 1980 to 1990), sediment models were coupled to the water column and hydrodynamic and watershed models were linked. A link was then established from watershed models to the input of the watershed. During the third stage (currently under way), airshed models are being incorporated with expansion to include other aspects of aquatic ecosystem. The Chesapeake Bay is used as an illustration. Issues of model credibility and confirmation are discussed; ultimately, the scientific and engineering community decides on the suitability of a modeling framework. The growth in model size over the history of modeling has been significant and parallels the increase in computing power. Future modeling challenges lie ahead in the areas of watershed models, airshed-watershed-estuarine-coastal ocean models, and whole ecosystem, living resources models. The success of water quality models will not necessarily be due to “bigness” and complexity but rather to increases in understanding, which can contribute to building consensus in water quality management decision-making.